update gradle config to latest snom API

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

app/build.gradle

@@ -1,4 +1,6 @@
 import com.github.spotbugs.snom.SpotBugsTask
+import com.github.spotbugs.snom.Confidence
+import com.github.spotbugs.snom.Effort
 import org.gradle.internal.jvm.Jvm
 
 buildscript {
@@ -442,8 +444,8 @@ jacoco {
 
 spotbugs {
     ignoreFailures = true // should continue checking
-    effort = "max"
-    reportLevel = "medium"
+    effort = Effort.MAX
+    reportLevel = Confidence.valueOf('MEDIUM')
 }
 
 tasks.withType(SpotBugsTask).configureEach { task ->